1. Field of the Invention
The present invention relates to a sheet handling device having a sheet-aligning rotary member, and more particularly, to a sheet post-handling device that sequentially receives sheets of copy paper and the like ejected from an image forming apparatus, such as a copying machine, a printer, or a laser beam printer, after image formation, and subjects the sheets to processes, such as alignment and binding, and ejects and stacks the sheets in a stacking section.
2. Description of the Related Art
In image forming apparatuses, such as printing machines, copying machines, and printers, sheets are conveyed for image formation, and are ejected and stacked in an ejection tray after image formation. For the purpose of stacking in alignment, the ejected sheets are aligned in the sheet width direction by a regulating means that is movable in that direction, and are aligned in the sheet feeding direction by a rotary paddle returning the sheet so as to contact an abutting section.
When the sheets are aligned in the sheet feeding direction by a rotary paddle, the amount of deflection of the rotary paddle increases as the number of sheets to be stacked increases, which also increases the contact pressure between the rotary paddle and the sheets. As a result, the sheets may buckle when in contact with the abutting section, or overload may be imposed on the motor.
If the contact pressure is set to be small so that the stacked sheets do not buckle, even when the number of sheets increases, since the returning force decreases, it is necessary to increase the number of revolutions of the rotary paddle, and to turn the rotary paddle a multiple number of turns to align a single sheet. This may result in insufficient time to align the sheets in the sheet width direction. Moreover, since the sheets are aligned in the sheet width direction while in contact with the rotary paddle, the alignment in the sheet width direction may not be smooth.
The rotary paddle produces the returning force from stiffness of the paddles. Since the paddles are generally made of resin material, such as polyurethane, stiffness is likely to change with environmental changes, such as temperature changes, thereby making the contact pressure unstable. Furthermore, when curled paper or the like is aligned by the paddles, the rear end of the paper may be caught by the guide surface of the paddle, which results in alignment failure.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet handling device and an image forming apparatus equipped with a sheet-aligning rotary member having superior aligning ability.
According to one aspect of the present invention, there is provided a sheet handling device including: a sheet stacking device; an ejection device for ejecting sheets to the sheet stacking device; at least one rotary member having an arc-shaped outer peripheral surface around a portion of its circumference; and a sheet end stopper for holding the ends of the sheets stacked in the sheet stacking device.
The rotary member may be movable in a direction substantially perpendicular to a sheet stacking surface of the sheet stacking device.
In accordance with one aspect of the invention, the rotary member includes a rotation shaft, a support member for supporting the rotation shaft in engagement therewith, a guide portion provided in the support member, and a slide guide device in engagement with the guide portion so as to support the support member slidably in a direction substantially perpendicular to the sheet stacking surface of the sheet stacking device.
In accordance with another aspect of the invention, when the circumferential length of the arc-shaped outer peripheral surface of the rotary member is l1, the length from a contact point between the sheet stacking surface of the sheet stacking device and the outer peripheral surface of the rotary member to the sheet end stopper is l2, and the length from an intersection of a line perpendicularly extending from the outer peripheral surface of the ejection device on the downstream side and the sheet stacking surface of the sheet stacking device to the sheet end stopper is l3, l1xe2x89xa7l2 and l2xe2x89xa7l3.
In accordance with still another aspect of the invention, the rotary member has a turning center on the outer peripheral side with respect to the rotation center. Furthermore, the rotary member has a support portion fixed to the rotation center, and an outer peripheral portion supported by the support portion so as to turn on the turning center with respect to the support portion.
A positioning portion may be provided in the support portion so that the outer peripheral portion aligns with a circle formed when the rotary member turns, and an urging device may be provided to urge the outer peripheral portion toward the positioning portion.
At least one of the rotary members may have a high-friction member on the outer peripheral surface thereof. The high-friction member may be detachable from the rotary member, and may be provided at at least two points symmetrical with respect to the ejection center of the sheets to be ejected from the ejection device. The high-friction member may be made of rubber.
According to another aspect of the present invention, there is provided an image forming apparatus comprising image forming means for forming an image on a sheet and a sheet handling device, including: a sheet stacking device; an ejection device for ejecting sheets with an image formed thereon to the sheet stacking device; at least one rotary member placed above the sheet stacking device and having an arc-shaped outer peripheral surface around a portion of a circumference of the rotary member; and a sheet end stopper for holding the ends of the sheets stacked in the sheet stacking device.
According to the above configuration, since the nearly arc-shaped rotary member is turned in contact with the stacked sheets, the amount of return of the sheets can be increased, and a single sheet can be aligned by one turn of the rotary member, which reduces the number of revolutions of the motor. Moreover, this ensures sufficient time for alignment in the sheet width direction. Since the rotary member is arc-shaped, it can be retracted from the sheet stacking space after alignment in the sheet feeding direction, which allows the sheets to be smoothly aligned in the sheet width direction without imposing a load.
Furthermore, since the rotary member has the pressure portion for raking the sheet, whose end remains on the guide surface below the ejection rollers, onto the sheet stacking surface, even curled paper and the like can be reliably aligned.
Even when the number of sheets to be stacked on the stacking device increases or decreases, since the rotary member can move in the direction of thickness of the stacked sheets, the contact pressure thereof does not significantly change and is made uniform, which can conform to a large number of stacked sheets.
As described above, according to the present invention, since the arc-shaped rotary member is turned in contact with the stacked sheets, it is possible to increase the amount of movement of the sheets.
Since the length of the arc-shaped outer peripheral portion of the rotary member is longer than the distance from the sheet landing position to the sheet end stopper, the sheet can be reliably moved to the sheet end stopper by only one turn of the rotary member.
Since the rotary member is movable in the direction of thickness of the sheets, the amount of change in contact pressure due to changes in the number of stacked sheets can be reduced, or a constant and stable alignment amount can be ensured regardless of the number of sheets.
Furthermore, even if a sheet ejected from the ejection device leans on the lower guide, it can be raked by the raking portion provided in the rotary member. This allows the sheet to reliably land on the handling tray and to be moved to the sheet end stopper.
Since the driving-side ejection roller is placed in the upper part of the path, and the return roller is placed in a small space between the path and the post-handling tray, the device can be reduced in size. Since the outer peripheral portion of the return roller is turnable on another center, multiple stacked sheets can be smoothly returned without causing step-out. Since the return roller can retract inside the rear end guide during alignment in the sheet width direction, smooth alignment can be achieved without imposing load. In addition, since the rubber members of the return rollers are placed symmetrically with respect to the sheet ejection center, the sheets can be prevented from skewing during returning operation. Since the rubber members are detachable, maintenance is facilitated.
Further objects, features, and advantages of the present invention will be apparent from the following description of the preferred embodiments with reference to the attached drawings.